U.S. patent application number 13/957660 was filed with the patent office on 2014-06-12 for cable compensation circuit.
The applicant listed for this patent is Fairchild Korea Semiconductor Ltd.. Invention is credited to Byunghak AHN, Keun-Eui HONG, Eunsung JANG, Jin-Tae KIM, Taesung KIM, Gwanbon KOO, Youngbae PARK, Jaehan YOON.
Application Number | 20140159678 13/957660 |
Document ID | / |
Family ID | 50266705 |
Filed Date | 2014-06-12 |
United States Patent
Application |
20140159678 |
Kind Code |
A1 |
PARK; Youngbae ; et
al. |
June 12, 2014 |
CABLE COMPENSATION CIRCUIT
Abstract
One cable compensation circuit is connected to a shunt regulator
to generate a feedback voltage corresponding to an output voltage
of a power supply device. The cable compensation circuit controls
cathode impedance of the shunt regulator according to the output
current of the power supply device to compensate a voltage drop
generated in a cable.
Inventors: |
PARK; Youngbae; (Bucheon-si,
KR) ; JANG; Eunsung; (Bucheon-si, KR) ; YOON;
Jaehan; (Bucheon-si, KR) ; AHN; Byunghak;
(Seoul, KR) ; KIM; Jin-Tae; (Seoul, KR) ;
KIM; Taesung; (Suwon-si, KR) ; KOO; Gwanbon;
(Bucheon-si, KR) ; HONG; Keun-Eui; (Cupertino,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Fairchild Korea Semiconductor Ltd. |
Buncheon |
|
KR |
|
|
Family ID: |
50266705 |
Appl. No.: |
13/957660 |
Filed: |
August 2, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61679173 |
Aug 3, 2012 |
|
|
|
61696367 |
Sep 4, 2012 |
|
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Current U.S.
Class: |
323/229 |
Current CPC
Class: |
H02M 3/33523 20130101;
G05F 1/10 20130101; H02M 2001/0025 20130101 |
Class at
Publication: |
323/229 |
International
Class: |
G05F 1/10 20060101
G05F001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 8, 2013 |
KR |
10-2013-0079957 |
Claims
1. A cable compensation circuit coupled to a first shunt regulator
configured to generate a feedback voltage corresponding to an
output voltage of a power supply device, the cable compensation
circuit comprising: a first node configured to provide a voltage
that is changed based on an output current of the power supply
device; and a diode coupled between the first node and a second
node, the second node being coupled to a reference terminal of the
first shunt regulator, wherein a cathode impedance of the first
shunt regulator is controlled based on a voltage of the second
node, and wherein a feedback voltage changes based on the cathode
impedance of the first shunt regulator.
2. The cable compensation circuit of claim 1, wherein the first
node is coupled to an anode of a rectifying diode to which output
current flows.
3. The cable compensation circuit of claim 2, further comprising: a
first resistor coupled between a cathode of the diode and the
second node; a second resistor having a first terminal coupled to
the second node and a second terminal coupled to a ground; and a
first transistor having a control terminal coupled to the second
node and a first terminal coupled to the reference terminal of the
first shunt regulator.
4. The cable compensation circuit of claim 3, further comprising a
first capacitor coupled between the second node and the ground.
5. The cable compensation circuit of claim 3, further comprising a
second capacitor coupled between the cathode of the diode and the
ground.
6. The cable compensation circuit of claim 5, further comprising a
third resistor coupled between the first terminal of the first
transistor and the reference terminal of the first shunt
regulator.
7. The cable compensation circuit of claim 3, further comprising: a
third resistor coupled between the second node and the control
terminal of the first transistor; and a fourth resistor coupled
between the first terminal of the first transistor and the
reference terminal of the first shunt regulator.
8. The cable compensation circuit of claim 3, further comprising: a
third resistor coupled between the second node and the control
terminal of the first transistor; a fourth resistor coupled between
the second node and the ground; and a fifth resistor coupled
between the first terminal of the first transistor and the
reference terminal of the first shunt regulator.
9. The cable compensation circuit of claim 8, wherein a temperature
change characteristic of the fourth resistor is opposite a
temperature change characteristic of the first transistor.
10. The cable compensation circuit of claim 3, further comprising:
a third resistor coupled between the second node and the control
terminal of the first transistor; a second transistor coupled
between the second terminal of the second resistor and the ground;
and a fourth resistor coupled between the first terminal of the
second transistor and the reference terminal of the first shunt
regulator.
11. The cable compensation circuit of claim 10, wherein a forward
voltage of the second transistor is configured to be decreased
based on a temperature change to compensate a current increase of
the second transistor based on the temperature change, or the
forward voltage of the second transistor is configured to be
increased based on the temperature change to compensate a current
decrease of the second transistor based on the temperature
change.
12. The cable compensation circuit of claim 2, further comprising:
a first resistor coupled between the cathode of the diode and the
second node; a second resistor having a first terminal coupled to
the second node and a second terminal coupled to a ground; and a
second shunt regulator coupled to the reference terminal of the
first shunt regulator, wherein current flowing to the second shunt
regulator is configured to be varied based on the voltage of the
second node and is configured to change the reference terminal
voltage of the second shunt regulator.
13. The cable compensation circuit of claim 12, wherein the
reference terminal of the second shunt regulator is coupled to the
second node, and the cable compensation circuit further comprises:
a third resistor coupled between the reference terminal of the
second shunt regulator and the cathode of the second shunt
regulator; and a fourth resistor coupled between the cathode of the
second shunt regulator and the reference terminal of the first
shunt regulator.
14. The cable compensation circuit of claim 12, further comprising
a first capacitor coupled between the second node and the
ground.
15. A cable compensation circuit coupled to a shunt regulator
configured to generate a feedback voltage corresponding to an
output voltage of a power supply device, the cable compensation
circuit comprising: a first node configured to provide a voltage
that is changed based on an output current of the power supply
device; and a diode coupled between the first node and an anode of
the shunt regulator, wherein a cathode impedance of the shunt
regulator is controlled based on a voltage of a second the node,
and wherein a feedback voltage changes based on the cathode
impedance of the shunt regulator.
16. The cable compensation circuit of claim 15, wherein the first
node is coupled to an anode of a rectifying diode to which output
current flows.
17. The cable compensation circuit of claim 15, further comprising:
a first resistor coupled between the second node and the ground;
and a capacitor coupled to the first resistor in parallel, wherein
the capacitor is configured to filter a noise of the voltage of the
second node.
18. A cable compensation circuit coupled to a shunt regulator
configured to generate a feedback voltage corresponding to an
output voltage of a power supply device, comprising: a first node
configured to provide a voltage that is changed based on an on
period of the power switch of the power supply device; and a first
diode coupled between a second node and a rectifying diode to which
an output current of the power supply device flows, wherein a
cathode impedance of the shunt regulator is controlled based on a
voltage of the second node, and wherein a feedback voltage changes
based on the cathode impedance of the shunt regulator.
19. The cable compensation circuit of claim 18, wherein the cathode
of the first diode is coupled to the anode of the rectifying diode,
and the cable compensation circuit further comprises: a first
resistor coupled between the anode of the first diode and the
second node; and a capacitor coupled between the second node and
the ground.
20. The cable compensation circuit of claim 19, wherein the anode
of the rectifying diode is coupled to a secondary coil of the power
supply device, and when a power switch of the power supply device
is turned on, the diode is configured to be turned on by the
voltage of the secondary coil.
21. The cable compensation circuit of claim 18, further comprising:
a second diode coupled between the cathode of the rectifying diode
and the second node; and a capacitor configured to store a
difference between a forward voltage of the rectifying diode
generated by the output current and a forward voltage of the second
diode.
22. The cable compensation circuit of claim 21, wherein the
capacitor is coupled between the second node and the ground, and a
forward voltage of the rectifying diode is increased by the
increase of the output current such that a negative voltage charged
to the capacitor is decreased.
23. The cable compensation circuit of claim 21, wherein: the
capacitor is coupled between the output voltage and the second
node; and the forward voltage of the rectifying diode is increased
based on the increase of the output current such that the voltage
of the second node is decreased based on the increase of the
voltage charged to the capacitor.
24. The cable compensation circuit of claim 23, further comprising:
a second resistor coupled between the anode of the second diode and
the second node; and a third resistor coupled between the output
voltage and the second node.
25. The cable compensation circuit of claim 18, further comprising:
an first resistor connected between the second node and the
reference terminal of the shunt regulator.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priorities to and the benefits of
U.S. Patent Application No. 61/679,173 filed in the USPTO on Aug.
3, 2012, and U.S. Patent Application No. 61/696,367 filed in the
USPTO on Sep. 4, 2012, and the priority and benefit of Korean
Patent Application No. 10-2013-0079957 filed in the Korean
Intellectual Property Office on Jul. 8, 2013, the entire contents
of which are incorporated herein by reference.
BACKGROUND
[0002] (a) Field
[0003] Embodiments relates to a cable compensation circuit for
compensating a voltage drop of a cable. For example, the cable
compensation circuit to compensate the voltage drop generated in
the cable is connected between a power supply device and a
battery.
[0004] (b) Description of the Related Art
[0005] A cable is connected between an output capacitor of a
charger and a battery. When the output current of the charger is
small, the voltage drop generated in the cable is not a problem.
However, when the output current is high (when a load is large),
the voltage drop generated in the cable is increased such that the
voltage supplied to the battery is decreased.
[0006] The output voltage of the charger is controlled as a rated
voltage to be suitable for battery charging, however the voltage
supplied to the battery is smaller than the rated voltage because
of the voltage drop of the cable.
[0007] The above information disclosed in this Background section
is only for enhancement of understanding of the background of the
invention and therefore it may contain information that does not
form the prior art that is already known in this country to a
person of ordinary skill in the art.
SUMMARY
[0008] A means compensating a voltage drop by a cable is
provided.
[0009] A cable compensation circuit according to an exemplary
embodiment compensates a voltage drop of a cable connected between
a power supply device and a load.
[0010] The cable compensation circuit includes a diode in which an
anode voltage is increased according to an increase of an output
current of the power supply device and at least two resistors
dividing the anode voltage.
[0011] Also, the cable compensation circuit includes a node in
which a voltage that is decreased according to an increase of the
output current of the power supply device is generated and a diode
connected to the node and a secondary side of the power supply
device, and the reference terminal of the shunt regulator of the
power supply device is connected to the node.
[0012] The cable compensation circuit increases the cathode
impedance of the shunt regulator of the power supply device as the
output current is increased. Energy transmitted to the secondary
side of the power supply device is increased according to the
increase of the cathode impedance of the shunt regulator.
[0013] The cable compensation circuit according to the present
invention is connected to the shunt regulator to generate the
feedback voltage corresponding to the output voltage of the power
supply device. The cable compensation circuit includes a first node
in which a voltage that is changed according to an output current
of the power supply device is generated and a diode connected
between the first node and a second node coupled to a reference
terminal of the shunt regulator, wherein a cathode impedance of the
shunt regulator is controlled according to a voltage of the second
node and a feedback voltage is changed according to the cathode
impedance of the shunt regulator.
[0014] The first node is connected to an anode of the rectifying
diode to which the output current flows.
[0015] The cable compensation circuit further includes a first
resistor connected between a cathode of the diode and the second
node, a second resistor including one terminal connected to the
second node and the other terminal coupled to a ground, and a
transistor including a control terminal coupled to the second node
and a first terminal coupled to the reference terminal of the shunt
regulator.
[0016] The cable compensation circuit may further include a first
capacitor connected between the second node and the ground.
[0017] The cable compensation circuit may further include a second
capacitor connected between the cathode of the diode and the
ground. The cable compensation circuit may further include a third
resistor connected between the first terminal of the transistor and
the reference terminal of the shunt regulator.
[0018] The cable compensation circuit may further include a fourth
resistor connected between the second node and the control terminal
of the transistor, and a fifth resistor connected between the first
terminal of the transistor and the reference terminal of the shunt
regulator.
[0019] The cable compensation circuit may further include a sixth
resistor connected between the second node and the control terminal
of the transistor, a seventh resistor connected between the second
node and the ground, and an eighth resistor connected between the
first terminal of the transistor and the reference terminal of the
shunt regulator. A temperature change characteristic of the seventh
resistor may be opposite to a temperature change characteristic of
the transistor.
[0020] The cable compensation circuit may further include an eighth
resistor connected between the second node and the control terminal
of the transistor, a first transistor connected between the other
terminal of the third resistor and the ground and diode-connected,
and a ninth resistor connected between the first terminal of the
transistor and the reference terminal of the shunt regulator. A
forward voltage of the first transistor is decreased according to
the temperature change to compensate the current increase of the
transistor according to the temperature change, or the forward
voltage of the first transistor is increased according to the
temperature change to compensate the current decrease of the
transistor according to the temperature change.
[0021] The cable compensation circuit may further include a tenth
resistor connected between the cathode of the diode and the second
node, an eleventh resistor including one terminal connected to the
second node and the other terminal coupled to the ground, and a
first shunt regulator coupled to the reference terminal of the
shunt regulator, and the current flowing to the first shunt
regulator is varied according to the voltage of the second node
such that the reference terminal voltage of the shunt regulator is
changed.
[0022] The reference terminal of the first shunt regulator is
connected to the second node, and the cable compensation circuit
further includes a twelfth resistor connected between the reference
terminal of the first shunt regulator and the cathode, and a
thirteenth resistor connected between the cathode of the first
shunt regulator and the reference terminal of the shunt
regulator.
[0023] The cable compensation circuit may further include a first
capacitor connected between the second node and the ground.
[0024] A cable compensation circuit according to the present
invention is connected to a shunt regulator to generate a feedback
voltage corresponding to an output voltage of a power supply
device, and includes: a third node in which a voltage that is
changed according to an output current of the power supply device
is generated; and a diode connected between the third node and an
anode of the shunt regulator, wherein a cathode impedance of the
shunt regulator is controlled according to a voltage of the third
node and a feedback voltage is changed according to the cathode
impedance of the shunt regulator.
[0025] The third node is connected to an anode of a rectifying
diode to which the output current flows.
[0026] The cable compensation circuit includes a fourteenth
resistor connected between the third node and the ground, and a
capacitor connected to the fourteenth resistor in parallel, wherein
the capacitor filters a noise of the voltage of the fourth
node.
[0027] A cable compensation circuit according to the present
invention is connected to a shunt regulator to generate a feedback
voltage corresponding to an output voltage of a power supply
device, and includes a third node in which a voltage that is
changed according to an on period of the power switch of the power
supply device is generated, and a diode coupled between a
rectifying diode to which an output current of the power supply
device flows and the fourth node, wherein a cathode impedance of
the shunt regulator is controlled according to a voltage of the
fourth node and a feedback voltage is changed according to the
cathode impedance of the shunt regulator.
[0028] The cathode of the diode is connected to the anode of the
rectifying diode, and the cable compensation circuit further
includes a fifteenth resistor connected between the anode of the
diode and the fourth node, and a capacitor connected between the
fourth node and the ground.
[0029] The anode of the rectifying diode is connected to the
secondary coil of the power supply device, and when the power
switch of the power supply device is turned on, the diode is turned
on by the voltage of the secondary coil.
[0030] The cable compensation circuit further includes a diode
connected between the cathode of the rectifying diode and the
fourth node, and a capacitor storing a difference between a forward
voltage of the rectifying diode generated by the output current and
a forward voltage of the diode.
[0031] The capacitor is connected between the fourth node and the
ground, and a forward voltage of the rectifying diode is increased
by the increase of the output current such that a negative voltage
charged to the capacitor is decreased.
[0032] The capacitor is connected between the output voltage and
the fourth node, and the forward voltage of the rectifying diode is
increased by the increase of the output current such that the
voltage of the fourth node is decreased according to the increase
of the voltage charged to the capacitor.
[0033] The cable compensation circuit may further include a
sixteenth resistor connected between the anode of the diode and the
fourth node, and a seventeenth resistor connected between the
output voltage and the fourth node.
[0034] The cable compensation circuit may further include an
eighteenth resistor connected between the fourth node and the
reference terminal of the shunt regulator.
[0035] The voltage drop of the cables is compensated by one among
the exemplary embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] FIG. 1 is a view of a cable compensation circuit according
to a first exemplary embodiment.
[0037] FIG. 2 is a view of a cable compensation circuit according
to a second exemplary embodiment.
[0038] FIG. 3 is a view of a cable compensation circuit according
to a third exemplary embodiment.
[0039] FIG. 4 is a view of a cable compensation circuit according
to a fourth exemplary embodiment.
[0040] FIG. 5 is a view of a cable compensation circuit according
to a fifth exemplary embodiment.
[0041] FIG. 6 is a view of a cable compensation circuit according
to a sixth exemplary embodiment.
[0042] FIG. 7 is a view of a cable compensation circuit according
to a seventh exemplary embodiment.
[0043] FIG. 8 is a waveform diagram to explain an operation of a
cable compensation circuit according to the seventh exemplary
embodiment.
[0044] FIG. 9 is a view of a cable compensation circuit according
to an eight exemplary embodiment.
[0045] FIG. 10 is a view of a cable compensation circuit according
to a ninth exemplary embodiment.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0046] In the following detailed description, only certain
exemplary embodiments have been shown and described, simply by way
of illustration. As those skilled in the art would realize, the
described embodiments may be modified in various different ways,
all without departing from the spirit or scope of the present
invention. Accordingly, the drawings and description are to be
regarded as illustrative in nature and not restrictive. Like
reference numerals designate like elements throughout the
specification.
[0047] Throughout this specification and the claims that follow,
when it is described that an element is "coupled" to another
element, the element may be "directly coupled" to the other element
or "electrically coupled" to the other element through a third
element. In addition, unless explicitly described to the contrary,
the word "comprise" and variations such as "comprises" or
"comprising" will be understood to imply the inclusion of stated
elements but not the exclusion of any other elements.
[0048] Now, a cable compensation circuit according to exemplary
embodiments will be described with reference to FIG. 1 to FIG.
10.
[0049] FIG. 1 is a view of a cable compensation circuit according
to the first exemplary embodiment. A cable compensation circuit 250
according to an exemplary embodiment is connected to a secondary
side of a power supply device 10 and controls an operation of a
feedback circuit according to a load.
[0050] The power supply device 10 includes a capacitor C1, a
transformer 100, a rectifying diode D1, output capacitors C2 and
C3, a power switch M, a gate driver 200, and a feedback circuit
400.
[0051] An input voltage Vin is smoothed by the capacitor C1 and is
transmitted to a primary side of the transformer 100.
[0052] The transformer 100 includes a primary coil CO1 and a
secondary coil CO2, and a coil ratio of the transformer is n:1 (a
winding number of CO1 to a winding of CO2).
[0053] One terminal of the primary coil CO1 is supplied with the
input voltage Vin and the other terminal of the primary coil CO1 is
connected to the power switch M. Energy stored to the primary coil
CO1 during an on period of the power switch M is transmitted to the
secondary coil CO2 in an off period of the power switch M.
[0054] A gate electrode of the power switch M is connected to an
output of the gate driver 200 and switching is performed according
to a gate voltage VG output from the gate driver 200. The power
switch M is an n channel type of transistor such that it is turned
on by a gate voltage VG of a high level and is turned off according
to a gate voltage VG of a low level.
[0055] The gate driver 200 generates the gate voltage VG according
to a feedback signal FB. For example, the gate driver 200 generates
the gate voltage VG for the energy transmitted to the secondary
side to be decreased as the voltage of the feedback signal FB is
decreased, and for the energy transmitted to the secondary side to
be increased as the voltage of the feedback signal FB is
increased.
[0056] The rectifying diode D1 is connected between one terminal of
the secondary coil CO2 and the output terminal, and is turned on
during the off period of the power switch M. The current
transmitted to the secondary side is transmitted to a load through
the rectifying diode D1.
[0057] In the first exemplary embodiment, a battery could be a load
as an example. The output terminal of the power supply device 10 is
connected to the battery through the cables CABLE1 and CABLE2. The
power supply device 10 may perform a charger function of supplying
a charging current to the battery. The output capacitors C2 and C3
are coupled in parallel to the output terminal of the power supply
device 10, the CABLE1 is connected to one terminal of the output
capacitors C2 and C3 and the (+) terminal of the battery, and the
CABLE2 is connected to the other terminal (a secondary side ground)
of the output capacitors C2 and C3 and the (-) terminal of the
battery.
[0058] The output capacitors C2 and C3 reduce a ripple of the
output voltage VO to smooth the output voltage VO.
[0059] The feedback circuit 400 generates a feedback signal
corresponding to the output voltage VO. The feedback circuit 400
includes an opto-coupler 410, a shunt regulator 420, four resistors
R1-R4, and two capacitors C4 and CFB. The opto-coupler 410 includes
an opto-diode 411 and an opto-transistor 412.
[0060] The output voltage VO is divided by the resistor R1 and the
resistor R2 and a reference voltage VR11 is generated. The shunt
regulator 420 includes a reference terminal input with the
reference voltage VR11, a cathode connected to the cathode of the
opto-diode 411, and an anode connected to a node NA.
[0061] The shunt regulator 420 generates a sink current according
to a difference between the reference voltage VR11 as the voltage
of a reference terminal and the voltage VA11 of the anode
(hereinafter, referring to a reference of the shunt regulator 420).
Accordingly, if the output voltage VO is increased, the current
sinking through the opto-diode 411 is increased by the shunt
regulator 420, and if the output voltage VO is decreased, the
current sinking through the opto-diode 411 is decreased by the
shunt regulator 420.
[0062] A gain of the shunt regulator 420 is determined by the
capacitor C4 and the resistor R3 that are connected in series
between the reference terminal of the shunt regulator 420 and the
cathode. The gain of the shunt regulator 420 is a ratio between the
reference terminal voltage change and the cathode voltage
change.
[0063] The resistor R4 is connected between the output voltage VO
and the anode of the opto-diode 411. The resistor R4 supplies a
bias current of the shunt regulator 420.
[0064] The current flowing to the opto-transistor 412 is
proportional to the current flowing to the opto-diode 411. The
capacitor CFB is connected in parallel to the opto-transistor 412.
As the current flowing to the opto-diode 411 is increased, the
current flowing to the opto-transistor 412 is increased and the
capacitor CFB is discharged according to the current increase of
the opto-transistor 412, and the voltage of the feedback signal FB
is decreased.
[0065] As the current flowing to the opto-diode 411 is decreased,
the current flowing to the opto-transistor 412 is decreased and the
capacitor CFB is charged according to the current decrease of the
opto-transistor 412, and the voltage of the feedback signal FB is
increased.
[0066] As the load is increased, the output voltage VO is decreased
such that the voltage of the feedback signal FB is increased. Thus,
the gate driver 200 controls the switching operation in the
direction that the energy transmitted to the secondary side is
increased. For example, the gate driver 200 may increase an on-duty
of the gate voltage VG.
[0067] As the load is decreased, the output voltage VO is increased
such that the voltage of the feedback signal FB is decreased. Thus,
the gate driver 200 controls the switching operation in the
direction that the energy transmitted to the secondary side is
decreased. For example, the gate driver 200 may decrease an on-duty
of the gate voltage VG.
[0068] The cable compensation circuit 250 decreases the reference
of the shunt regulator 420 as the output current IO is increased
such that the cathode impedance of the shunt regulator 420 is
increased. Thus, the current flowing to the opto-diode 411 is
decreased such that the energy transmitted to the secondary side is
increased.
[0069] That is, the cable compensation circuit 250 controls the
voltage between the reference terminal of the shunt regulator 420
and the anode to control the voltage of the feedback signal FB. The
cable compensation circuit 250 includes a diode DC11, a resistor
R5, a resistor R6, and a capacitor C5.
[0070] The diode DC11 is connected to the output terminal of the
power supply device 10. In detail, the diode DC11 includes an anode
connected to the anode of the rectifying diode D1 and one terminal
of the secondary coil CO2, and a cathode connected to one terminal
of the resistor R5. The anode voltage of the diode DC11 is changed
according to the output current IO supplied to the load. For
example, as the output current IO is increased, the anode voltage
VA12 of the diode DC11 is also increased, and as the output current
IO is decreased, the anode voltage VA12 of the diode DC11 is also
decreased.
[0071] The resistor R5 is connected between the cathode of the
diode DC11 and the node NA, the resistor R6 is connected between
the node NA and the secondary side ground, and the capacitor C5 is
connected to the resistor R6 in parallel. The capacitor C5 filters
a noise of the anode voltage VA11.
[0072] The anode voltage VA12 is divided by the resistor R5 and the
resistor R6 such that the voltage of the node NA, that is, the
anode voltage VA11, is determined. The current flowing to the shunt
regulator 420 is determined according to the difference between the
reference voltage VR11 and the anode voltage VA11 of the shunt
regulator 420.
[0073] Accordingly, if the anode voltage VA12 is increased by the
increase of the output current IO, the anode voltage VA11 is also
increased, and the difference between the reference voltage VR11 of
the reference terminal of the shunt regulator 420 and the anode
voltage VA11, that is, the reference of the shunt regulator 420, is
decreased. Thus, the voltage of the feedback signal FB is increased
compared with a conventional art not having the cable compensation
circuit 250.
[0074] As the voltage of the feedback signal FB becomes higher, the
energy transmitting to the secondary side is increased such that
the energy transmitted to the secondary side is further increased
compared with the conventional art. Accordingly, the voltage drop
generated in the cables CABLE1 and CABLE2 are compensated according
to the increase of the output current IO. That is, to maintain the
voltage supplied to the battery as the rated voltage, the output
voltage VO is increased to a level at which the voltage drop is
compensated.
[0075] According to the first exemplary embodiment, the anode
voltage VA11 is increased according to the increase of the output
current IO such that the voltage of the feedback signal FB is
increased, and thereby the energy transmitted to the secondary side
is also increased. Accordingly, the increase of the voltage drop
generated in the cables CABLE1 and CABLE2 according to the increase
of the output current IO is compensated by an exemplary
embodiment.
[0076] The cable compensation circuit may have numerous variations,
and the present invention is not limited to the exemplary
embodiment shown in FIG. 1. That is, the cable compensation circuit
increases the cathode impedance of the shunt regulator 420
according to the increase of the output current IO such that the
current flowing to the opto-diode is decreased, thereby realizing
the circuit increasing the energy transmitted to the secondary
side.
[0077] For example, in the exemplary embodiment of FIG. 1, the
cable compensation circuit increases the anode voltage VA11 of the
shunt regulator 420 according to the increase of the output current
IO. Alternately, the reference voltage of the reference terminal of
the shunt regulator 420 may be decreased according to the increase
of the output current IO, thereby decreasing the reference of the
shunt regulator 420.
[0078] FIG. 2 is a view of a cable compensation circuit according
to the second exemplary embodiment.
[0079] Compared with the above exemplary embodiment, the
overlapping components are indicated by the same reference numerals
and the overlapping description is omitted. As shown in FIG. 2, a
cable compensation circuit 270 according to the second exemplary
embodiment is connected to the secondary side of a power supply
device 20 to control the operation of the feedback circuit
according to the load.
[0080] Compared with FIG. 1, the anode of the shunt regulator 420
is not connected to the cable compensation circuit but is directly
connected to the secondary side ground, and the reference terminal
of the shunt regulator 420 is connected to the cable compensation
circuit 270.
[0081] The cable compensation circuit 270 also decreases the
reference of the shunt regulator 420 as the output current IO is
increased such that the cathode impedance of the shunt regulator
420 is increased. Thus, the current flowing through the opto-diode
411 is decreased such that the energy transmitted to the secondary
side is increased.
[0082] As shown in FIG. 2, the cable compensation circuit 270
controls the base voltage of a BJT Q according to the anode voltage
VA13 thereby controlling the reference terminal voltage VR1 of the
shunt regulator 420.
[0083] The cable compensation circuit 270 includes a diode DC12, a
resistor R7, a resistor R8, a resistor R9, the BJT Q, and a
capacitor C6.
[0084] The diode DC12 is connected to the output terminal of the
power supply device 20. In detail, the anode of the diode DC12 is
connected to the anode of the rectifying diode D1 of the secondary
side and one terminal of the secondary coil CO2, and the cathode of
the diode DC12 is connected to one terminal of the resistor R7 and
one terminal of the capacitor C6.
[0085] An anode voltage VA13 of the diode DC12 is changed according
to the output current IO supplied to the load. For example, as the
output current IO is increased, the anode voltage VA13 is also
increased, and as the output current 10 is decreased, the anode
voltage VA13 is also decreased.
[0086] The resistor R8 is connected between the other terminal of
the resistor R7 and the secondary side ground. The voltage VNR of
the node NR of the resistors R7 and R8 is applied to the base of
the BJT Q.
[0087] The capacitor C6 is connected between the cathode of the
diode DC12 and the secondary side ground to filter the noise of the
voltage VNR.
[0088] The emitter of the BJT Q is connected to the secondary side
ground, and the collector thereof is connected to one terminal of
the resistor R9. The other terminal of the resistor R9 is connected
to the reference terminal of the shunt regulator 420.
[0089] The anode voltage VA13 is divided by the resistor R7 and the
resistor R8 thereby determining the voltage of the node NR, that
is, the voltage VNR. The current flowing to the BJT Q is determined
according to the voltage VNR, and as the current flowing to the BJT
Q is increased, the reference terminal voltage of the shunt
regulator 420, that is, the reference voltage VR1 is decreased.
[0090] The current flowing to the shunt regulator 420 is determined
according to the reference of the shunt regulator 420, that is, the
difference between the reference voltage VR1 and the anode voltage
of the shunt regulator 420. In another exemplary embodiment, the
anode voltage of the shunt regulator 420 is the ground level.
Accordingly, the current flowing to the shunt regulator 420 is
determined according to the reference voltage VR1.
[0091] If the anode voltage VA13 is increased by the increase of
the output current IO, the voltage VNR is increased and the
reference voltage VR1 is decreased. Thus, the voltage of the
feedback signal FB is increased compared with the conventional art
not having the cable compensation circuit 270.
[0092] As the voltage of the feedback signal FB is increased, the
energy transmitted to the secondary side is increased such that the
energy transmitted to the secondary side is further increased
compared with the conventional art. Accordingly, the voltage drop
generated in the cables CABLE1 and CABLE2 is compensated according
to the increase of the output current IO. That is, to maintain the
voltage supplied to the battery as the rated voltage, the output
voltage VO is increased to the level at which the voltage drop is
compensated.
[0093] Like the previous exemplary embodiment, in the second
exemplary embodiment, the anode voltage VA13 is increased according
to the increase of the output current IO such that the voltage of
the feedback signal FB is increased, thereby also increasing the
energy transmitted to the secondary side. Accordingly, the increase
of the voltage drop generated in the cables CABLE1 and CABLE2
according to the increase of the output current IO is compensated
by another exemplary embodiment.
[0094] FIG. 3 is a view of a cable compensation circuit according
to the third exemplary embodiment. The cable compensation circuit
300 according to the third exemplary embodiment is connected to the
secondary side of the power supply device 1 thereby controlling the
operation of the feedback circuit according to the load.
[0095] The same components as in the previous exemplary embodiment
are indicated by the same reference numerals and the overlapping
description is omitted.
[0096] The power supply device 1 includes the capacitor C1, the
transformer 100, the rectifying diode D1, the output capacitors C2
and C3, the power switch M, the gate driver 200, and the feedback
circuit 400, and is connected to the cable compensation circuit
300.
[0097] The output voltage VO is divided by the resistors R1 and R2
to generate the reference voltage VR1. The voltage of the reference
terminal of the shunt regulator 420 is referred to as the reference
voltage VR1, like in the second exemplary embodiment.
[0098] The cable compensation circuit 300 controls the cathode
impedance of the shunt regulator 420 according to the output
current IO. For example, the cable compensation circuit 300
decreases the reference of the shunt regulator 420 as the output
current IO is increased such that the cathode impedance of the
shunt regulator 420 is increased. Thus, the current flowing to the
opto-diode 411 is decreased such that the energy transmitted to the
secondary side is increased.
[0099] The output current IO means the load current supplied to the
load (the battery in an exemplary embodiment).
[0100] That is, the cable compensation circuit 300 controls the
reference terminal voltage of the shunt regulator 420 thereby
controlling the voltage of the feedback signal FB. The cable
compensation circuit 300 controls the base voltage of the BJT Q1
according to the anode voltage VA1 to control the reference
terminal voltage VR1 of the shunt regulator 420.
[0101] The cable compensation circuit 300 includes the diode DC1,
four resistors R11, R12, R13, and R14, the BJT Q1, and the
capacitor C11. The diode DC1 is connected to the output terminal of
the power supply device 1. In detail, the anode of the diode DC1 is
connected to the anode of the rectifying diode D1 of the secondary
side and one terminal of the secondary coil CO2, and the cathode of
the diode DC1 is connected to one terminal of the resistor R11.
[0102] The anode voltage VA1 of the diode DC1 is changed according
to the output current IO supplied to the load. For example, as the
output current IO is increased, the anode voltage VA1 is also
increased, and as the output current IO is decreased, the anode
voltage VA1 is also decreased.
[0103] One terminal of the resistor R12 is connected to the other
terminal of the resistor R11, and the other terminal of the
resistor R12 is connected to the secondary side ground. The voltage
VNR1 of the node NR1 connected to the resistors R11 and R12 is
applied to the base of the BJT Q1 through the resistor R14.
[0104] The capacitor C11 is connected between the node NR1 and the
secondary side ground thereby smoothing the voltage VNR1.
[0105] The emitter of the BJT Q1 is connected to the secondary side
ground, and the collector thereof is connected to one terminal of
the resistor R13. The other terminal of the resistor R13 is
connected to the reference terminal of the shunt regulator 420.
[0106] After the anode voltage VA1 is rectified by the diode DC1,
it is divided by the resistor R11 and the resistor R12, thereby
determining the voltage of the node NR1, that is, the voltage VNR1.
The current flowing to the BJT Q1 is determined according to the
voltage VNR1, and as the current flowing to the BJT Q1 is
increased, the reference terminal voltage of the shunt regulator
420, that is, the reference voltage VR1, is decreased.
[0107] The current flowing to the shunt regulator 420 is determined
by the reference of the shunt regulator 420, that is, the
difference between the reference voltage VR1 and the anode voltage
of the shunt regulator 420. In the third exemplary embodiment, the
anode voltage of the shunt regulator 420 is the ground level.
Accordingly, the current flowing to the shunt regulator 420 is
determined according to the reference voltage VR1.
[0108] If the anode voltage VA1 is increased by the increase of the
output current IO, the voltage VNR1 is increased and the reference
voltage VR1 is decreased. Thus, the voltage of the feedback signal
FB is increased compared with the conventional art not having the
cable compensation circuit 300.
[0109] As the voltage of the feedback signal FB is increased, the
energy transmitted to the secondary side is increased such that the
energy transmitted to the secondary side is further increased
compared with the conventional art. Accordingly, the voltage drop
generated in the cables CABLE1 and CABLE2 is compensated according
to the increase of the output current IO. That is, the output
voltage VO is increased such that the voltage drop generated in the
cables is compensated, and the voltage supplied to the battery is
maintained as the rated voltage.
[0110] The cable compensation circuit according to the fourth
exemplary embodiment further includes a resistor compensating a
variation according to a temperature change of the BJT.
[0111] FIG. 4 is a view of a cable compensation circuit according
to the fourth exemplary embodiment.
[0112] As shown in FIG. 4, a cable compensation circuit 310
according to the fourth exemplary embodiment is connected to the
secondary side of a power supply device 2 to control the operation
of the feedback circuit according to the load.
[0113] The cable compensation circuit 310 further includes the
diode DC2, five resistors R21-R25, and the capacitor C21. Compared
with the cable compensation circuit shown in FIG. 3, the resistor
R24 connected between the base of the BJT Q2 and the ground is
further included.
[0114] The cable compensation circuit 310 further includes the
resistor R24 to compensate the temperature deviation of the BJT Q2.
When the current flowing to the BJT Q2 is changed according to the
temperature change, the resistor to compensate the change is
connected to the base of the BJT Q2. The resistance of the resistor
R24 is changed according to the temperature.
[0115] The anode voltage VA2 of the diode DC2 is increased as the
output current IO is increased, and as the output current IO is
decreased, it is decreased. The resistor R21 is connected between
the cathode of the diode DC2 and the node NR2. The resistor R22,
the resistor R24, and the capacitor C21 are connected between the
node NR2 and the ground. The resistor R25 is connected between the
node NR2 and the base of the BJT Q2.
[0116] The current applied to the base of the BJT Q2 is changed
according to the voltage VNR2 of the node NR2. The capacitor C21
smoothes the voltage VNR2.
[0117] The emitter of the BJT Q2 is connected to the secondary side
ground, and the collector thereof is connected to one terminal of
the resistor R23. The other terminal of the resistor R23 is
connected to the reference terminal of the shunt regulator 420.
[0118] The anode voltage VA2 is rectified by the diode DC2 and is
divided by the resistors R21 and R22 such that the voltage VNR2 is
determined. The current flowing to the BJT Q2 is determined
according to the voltage VNR2, and as the current flowing to the
BJT Q2 is increased, the reference terminal voltage of the shunt
regulator 420, that is, the reference voltage VR1, is
decreased.
[0119] To prevent the current flowing to the BJT Q2 from being
changed according to the temperature change, the resistor R24 has a
temperature change characteristic that is opposite to the
temperature change characteristic of the BJT Q2.
[0120] For example, when the current flowing to the BJT Q2 is
increased according to the increase of the temperature, the
resistor R24 is realized for the resistance thereof to be decreased
according to the temperature increase. Thus, when the temperature
is increased, the resistance of the resistor R24 is decreased such
that the base voltage is decreased. Accordingly, the increase of
the current flowing to the BJT Q2 may be prevented.
[0121] In contrast, when the current flowing to the BJT Q2 is
decreased according to the temperature decrease, the resistor R24
may be realized for the resistance thereof to be increased
according to the temperature decrease. Thus, when the temperature
is decreased, the resistance of the resistor R24 is increased such
that the base voltage is increased. Accordingly, the decrease of
the current flowing to the BJT Q2 may be prevented.
[0122] The cable compensation circuit according to the fifth
exemplary embodiment may compensate the deviation according to the
temperature change of the BJT by using the BJT instead of the
resistor 24 of the fourth exemplary embodiment.
[0123] FIG. 5 is a view of a cable compensation circuit according
to the fifth exemplary embodiment.
[0124] As shown in FIG. 5, a cable compensation circuit 320
according to the fifth exemplary embodiment is connected to the
secondary side of a power supply device 3 to control the operation
of the feedback circuit according to the load.
[0125] The cable compensation circuit 320 includes the diode DC3,
four resistors R31-R34, the capacitor C31, the BJT Q31, and the BJT
Q32. As shown in FIG. 5, the cable compensation circuit 320 further
includes the BJT 32 of which the collector and the base are
connected.
[0126] The deviation of the BJT 32 according to the temperature
change is similar to the deviation of the BJT Q31. The base voltage
of the BJT Q31 is controlled by the BJT Q32 such that the current
flowing to the BJT Q31 according to the temperature change is not
changed.
[0127] The anode of the diode DC3 is connected to the anode voltage
VA3, and the cathode of the diode DC3 is connected to one terminal
of the resistor R31. The other terminal of the resistor R31 is
connected to the node NR3.
[0128] The capacitor C31 is connected between the node NR3 and the
ground to smooth the voltage VNR3.
[0129] One terminal of the resistor R32 and one terminal of the
resistor R33 are connected to the node NR3, and the collector of
the BJT Q32 is connected to the other terminal of the resistor R32.
The emitter of the BJT Q32 is connected to the secondary side
ground.
[0130] The other terminal of the resistor R33 is connected to the
base of the BJT Q31, and the collector of the BJT Q31 is connected
to the reference terminal of the shunt regulator 420 through the
resistor R34. The emitter of the BJT Q31 is connected to the
secondary side ground.
[0131] The anode voltage VA3 is rectified by the diode DC3 and is
divided by the resistors R31 and R32 and the on-resistance of the
BJT Q32 such that the voltage VNR3 is determined. The voltage VNR3
is transmitted to the base of the BJT Q31 through the resistor
R33.
[0132] The current flowing to the BJT Q31 is determined according
to the voltage VNR3, and as the current flowing to the BJT Q31 is
increased, the reference terminal voltage of the shunt regulator
420, that is, the reference voltage VR1, is decreased.
[0133] A forward voltage of the BJT Q32 used like a diode is
changed according to the temperature change such that the voltage
VNR3 is changed.
[0134] For example, if the forward voltage of the BJT Q32 is
decreased according to the temperature increase, the equivalent
resistance connected to the node NR3 is decreased such that the
voltage VNR3 is decreased. That is, the base voltage of the BJT Q31
is decreased.
[0135] When the current flowing to the BJT Q31 is increased
according to the temperature increase, the base voltage of the BJT
Q31 is decreased such that the current increase of the BJT Q31 may
be suppressed.
[0136] In contrast, if the on-resistance of the BJT Q32 is
increased according to the temperature decrease, the equivalent
resistance connected to the node NR3 is increased such that the
voltage VNR3 is increased. That is, the base voltage of the BJT Q31
is increased.
[0137] When the current flowing to the BJT Q31 is decreased
according to the temperature decrease, the base voltage of the BJT
Q31 is increased such that the current decrease of the BJT Q31 may
be suppressed.
[0138] Differently, the second to fifth exemplary embodiments may
use the shunt regulator instead of the BJT.
[0139] The cable compensation circuit according to the sixth
exemplary embodiment includes the shunt regulator instead of the
BJT.
[0140] FIG. 6 is a view of a cable compensation circuit according
to the sixth exemplary embodiment.
[0141] As shown in FIG. 6, a cable compensation circuit 330
according to the sixth exemplary embodiment is connected to the
secondary side of a power supply device 4 such that the operation
of the feedback circuit is controlled according to the load.
[0142] The cable compensation circuit 330 includes the diode DC4,
four resistors R41-R44, a shunt regulator 331, and the capacitor
C41.
[0143] The anode of the diode DC4 is connected to the anode voltage
VA4 and the cathode of the diode DC4 is connected to one terminal
of the resistor R41. The other terminal of the resistor R41 is
connected to the node NR4.
[0144] The capacitor C41 is connected between the node NR4 and the
ground thereby smoothing the voltage VNR4.
[0145] The resistor R42 is connected between the node NR4 and the
ground. The reference terminal of the shunt regulator 331 is
connected to the node NR4, the cathode of the shunt regulator 331
is connected to the reference terminal of the shunt regulator 420
through the resistor R44, and the anode of the shunt regulator 331
is connected to the secondary side ground.
[0146] The resistor R43 is connected between the reference terminal
and the cathode of the shunt regulator 331.
[0147] The anode voltage VA4 is rectified by the diode DC4 and then
divided by the resistors R41 and R42 such that the voltage VNR3 is
determined. The voltage VNR3 is input to the reference terminal of
the shunt regulator 331. The shunt regulator 331 is turned on if
the voltage of the reference terminal is more than a predetermined
voltage such that the current flows from the cathode to the anode
according to the voltage of the reference terminal.
[0148] As the output current IO is increased, the voltage VNR4 is
increased, and as the voltage VNR4 is increased, the current
flowing to the shunt regulator 331 is increased. As the current
flowing to the shunt regulator 331 is increased, the reference
voltage VR1 of the shunt regulator 420 is decreased.
[0149] The second to the sixth exemplary embodiment uses the BJT or
the shunt regulator generating the current according to the output
current IO controlling the cathode impedance of the shunt
regulator.
[0150] However, the present invention is not limited thereto, and
like the first exemplary embodiment, another exemplary embodiments
may have a circuit structure in which the output current IO
directly influences the cathode impedance of the shunt
regulator.
[0151] The cable compensation circuit of the seventh to ninth
exemplary embodiments does not include the BJT or the shunt
regulator.
[0152] FIG. 7 is a view of a cable compensation circuit according
to the seventh exemplary embodiment.
[0153] As shown in FIG. 7, the cable compensation circuit 500
according to the seventh exemplary embodiment is connected to the
secondary side of a power supply device 5 such that the operation
of the feedback circuit is controlled according to the load.
[0154] As shown in FIG. 7, the cable compensation circuit 500
includes a diode DC5, two resistors R51 and R52, and a capacitor
C51.
[0155] The diode DC5 includes the cathode connected to one terminal
of the secondary coil CO2, and the anode of the rectifying diode D1
and the anode connected to one terminal of the resistor R51.
[0156] The other terminal of the resistor R51 is connected to one
terminal of the resistor R52 and one terminal of the capacitor C51.
The other terminal of the capacitor C51 is connected to the ground
and the other terminal of the resistor R52 is connected to the
reference terminal of the shunt regulator 420.
[0157] FIG. 8 is a waveform diagram to explain an operation of a
cable compensation circuit according to the seventh exemplary
embodiment.
[0158] FIG. 8 shows a gate voltage VG, a drain-source voltage VDS,
a secondary side voltage VL2, an assistance voltage VAUX, and a
voltage VNR5.
[0159] The power switch M is turned on during a period in which the
gate voltage VG is the high level, and the power switch M is turned
off during a period in which the gate voltage VG is the low
level.
[0160] The drain-source voltage VDS of the power switch M at a
turn-off time TO of the power switch M is expressed by Equation
1.
VDS(T0)=(VO+VF)*n+Vin [Equation 1]
where VO is the output voltage, VF is the forward voltage of the
rectifying diode D1, n is the turns ratio, and Vin is the input
voltage.
[0161] When the energy stored in the primary coil CO1 is exhausted
among the turn-off period T1 and a resonance is started, as shown
in FIG. 8, the drain-source voltage VDS starts to resonate. During
the turn-on period T5 of the power switch M, the drain-source
voltage becomes zero voltage.
[0162] During the off period T1, the voltage VL2 of the secondary
coil CO2 is maintained as a sum of the output voltage VO and the
forwarding voltage VF, and then starts to resonate. As shown in
FIG. 8, the periods T2, T3, and T4 in which the voltage VL2 becomes
the negative voltage are generated. During the on period T5, the
voltage VL2 is a negative voltage of which the input voltage Vin is
divided by the turns ratio n.
[0163] The auxiliary voltage VAUX is the voltage of the node where
the anode of the diode DC5 and one terminal of the resistor R51 are
connected. In the blocking state of the diode DC5, the auxiliary
voltage VAUX is maintained as the 0 voltage.
[0164] At the period in which the voltage VL2 is the negative
voltage, the diode DC5 is turned on. Thus, the auxiliary voltage
VAUX is the voltage of the same waveform as the voltage VL2.
[0165] The voltage VNR5 of the node NR5 during the on period T5 of
the power switch M, as shown in FIG. 8, is charged and decreased in
the negative direction at the negative voltage region by the
auxiliary voltage VAUX (an absolute value is increased). During the
off period T1 of the power switch M, the voltage VNR5 is charged
and increased in the positive direction in the negative voltage
region (an absolute value is decreased).
[0166] If the output power is increased, that is, the output
current IO is increased, the on period is increased such that the
voltage VNR5 is further charged and decreased in the negative
direction at the negative region. Thus, the reference terminal
voltage of the shunt regulator 420, that is, the reference voltage
VR1 is further reduced.
[0167] FIG. 9 is a view of a cable compensation circuit according
to the eighth exemplary embodiment.
[0168] As shown in FIG. 9, the cable compensation circuit 510
according to the eighth exemplary embodiment is connected to the
secondary side of the power supply device 6 to control the
operation of the feedback circuit according to the load.
[0169] In FIG. 9, the rectifying diode D2 is connected between the
secondary side ground and the other terminal of the secondary coil
CO2. During the on period of the power switch M, the other terminal
voltage of the secondary coil CO2 is higher than the anode voltage
of the rectifying diode D2, that is, the secondary side ground.
Accordingly, the rectifying diode D2 is blocked such that the
current does not flow through the diode D2. During the off period
of the power switch M, the rectifying diode D2 is turned on such
that the current is supplied to the load.
[0170] The cable compensation circuit 510 includes the diode DC6,
the resistor R61, and the capacitor C61.
[0171] The diode DC6 includes the cathode connected to the other
terminal of the secondary coil CO2 and the anode connected to one
terminal of the capacitor C61. The other terminal of the capacitor
C61 is connected to the secondary side ground. The resistor R61 is
connected between the node NR6 and the reference terminal of the
shunt regulator 420. The capacitor C61 stores a difference between
the forward voltages of two diodes.
[0172] The operation of the cable compensation circuit 510
according to the eighth exemplary embodiment is as follows.
[0173] That is, as the voltage VNR6 of the node NR6 increases, the
difference between a change amount of the forward voltage of the
rectifying diode D2 according to the output current IO and the
forward voltage of the diode DC6 that is almost constant appears as
the negative voltage. That is, if the output current IO is
increased, the forward voltage of the diode D2 is increased such
that the voltage VNR6 of the node NR6 is further reduced. Thus, the
reference voltage VR1 is decreased according to the increase of the
output current IO.
[0174] FIG. 10 is a view of a cable compensation circuit according
to the ninth exemplary embodiment.
[0175] As shown in FIG. 10, the cable compensation circuit 520
according to the ninth exemplary embodiment is connected to the
secondary side of the power supply device 7 to control the
operation of the feedback circuit according to the load.
[0176] The cable compensation circuit 520 includes the diode DC7,
three resistors R71, R72, and R73, and the capacitor C71.
[0177] The diode DC7 includes the cathode connected to the other
terminal of the secondary coil CO2 and the anode connected to one
terminal of the resistor R72. The other terminal of the resistor
R72 is connected to one terminal of the resistor R71. The other
terminal of the resistor R71 is connected to the output voltage VO.
The voltage VNR7 of the node NR7 to which the resistor R71 and the
resistor R72 are connected between the reference terminal of the
shunt regulator 420 through the resistor R73. The capacitor C71 is
connected between the output voltage VO and the node NR7 thereby
smoothing the voltage VNR7.
[0178] After the power switch M is turned off, while the rectifying
diode D2 is turned on, the voltage of both terminals of the
capacitor C71 is increased. As the output current IO is increased,
the turn-on time of the rectifying diode D2 becomes longer such
that the voltage of both terminals of the capacitor C71 is further
increased. The voltage VNR7 of the node NR7 is a value of which the
voltage of both terminals of the capacitor C71 is subtracted from
the output voltage VO such that the voltage VNR7 of the node NR7 is
decreased according to the increase of the load. Thus, the
reference voltage VR1 is also decreased according to the increase
of the output current IO.
[0179] In the described exemplary embodiments, the cathode
impedance of the shunt regulator is increased according to the
increase of the output current IO such that the energy transmitted
to the secondary side is increased. Accordingly, the voltage drop
generated in the cables CABLE1 and CABLE2 according to the increase
of the output current IO may be compensated.
[0180] When providing a detecting resistor at a path where the
output current IO flows to sense the output current IO, power
consumption may be generated in the detecting resistor. Differently
from an exemplary embodiment, when using a primary side regulation
method, an additional coil to sense the information for the output
terminal must be provided such that the complexity and the size of
the transformer are increased.
[0181] According to the exemplary embodiments, the unnecessary
power consumption may be prevented without increasing of the size
and the complexity of the transformer, and the circuit compensating
the voltage drop generated in the cables is provided.
[0182] While this invention has been described in connection with
what is presently considered to be practical exemplary embodiments,
it is to be understood that the invention is not limited to the
disclosed embodiments, but, on the contrary, is intended to cover
various modifications and equivalent arrangements included within
the spirit and scope of the appended claims.
[0183] Also, in the appended claims, the ordinal numbers described
along with the elements do not to express the orders thereof, but
are used only to distinguish the elements described with the same
words.
DESCRIPTION OF SYMBOLS
[0184] power supply device 10, 20, 1-7 [0185] capacitor C1, C4, C5,
C6, CFB, C11, C21, C31, C41, C51, C61, C71 [0186] transformer 100
[0187] cable compensation circuit 250, 270, 300, 310, 320, 330,
500, 510, 520 [0188] rectifying diode D1, output capacitor C2 and
C3, power switch M [0189] gate driver 200, feedback circuit 400,
primary coil CO1 [0190] secondary coil CO2, opto-coupler 410 [0191]
shunt regulator 420 and 331 [0192] resistor R1-R9, R11-R14,
R21-R25, R31-R34 [0193] resistor R41-R44, R51, R52, R61, R71-R73
[0194] opto-diode 411, opto-transistor 412 [0195] diode DC11, DC12,
DC1-DC7 [0196] BJT Q1, Q2, Q31, Q32, Q
* * * * *